Percolation System - Remediation of Soils Contaminated with Mineral Oil

The problem

Fig.: Treatment basin in the soil treatment plant in Hirschfeld (Germany)

The challenge of the research project was the construction of a biological soil treatment centre with a percolation system on a former silage facility site.

One of the objectives was the optimisation of the living conditions of the autochthone microorganisms taking advantage of their capability to degrade pollutants. Although percolation systems are much more complex in construction than simple biopiles process control offers the opportunity of influencing the treatment process in various ways.

Thus, higher degradation rates reduce both the treatment time and the operational costs significantly, resulting in a more effective performance of the treatment facility.

The technique

In the treatment plant, the former silage basins are used as a fixed-bed reactor being filled with the polluted material. Each basin has a capacity of 750 tons of soil. The former seepage tank of the silage facility contains the bioreactor providing the process water that is applied to the soil’s surface. The process water infiltrates the soil heaps, is then collected by the drainage system and returned to the bioreactor. In co-current flow with the process water a defined air volume passes the treated material.

Fig.: Soil treatment plant in Hirschfeld (near Freiberg, Germany) providing a biological treatment of soils contaminated with mineral oil

The advantages

Percolation of the process water ensures favourable living conditions for microorganisms in soil. Over the whole treatment period, the material is kept moist in an optimal range of pH and fed with mineral nutrients. The aeration of the soil provides for the oxygen supply of the microorganisms.

Practical application

Practically, the soil temperature plays an important role in the degradation of contaminants, especially during winter. Combining measures of soil heating and heat loss prevention the degradation rate of mineral oil can be increased significantly.

In the soil treatment centre of our partner BAUER und MOURIK Umwelttechnik GmbH in Hirschfeld, the percolation system is in routine operation since 1998

The project was funded by the Deutsche Bundesstifung Umwelt (DBU).

Remediation of mineral oil contaminated soils by the percolation system - detailed information is available in German only.